1. Field of the Invention
This invention relates to a commercial convection oven having an easily tuneable high pressure airflow pattern. The convection oven has a duct with nozzles that extend into a cooking chamber. Each nozzle is positionable between an open position and a closed position in order to tune the airflow pattern within the cooking chamber while maintaining a desired static pressure within the duct.
2. Description of the Related Art
Conventional commercial convection ovens have one or more fans which circulate the air within the oven cavity. The airflow within the oven cavity is highly turbulent but characterized by a circulation pattern evident in the oven""s baking performance. A distinct and often undesirable pattern is seen on the cooked food product. In areas of the oven cavity where the airflow is too low, the food product will be raw or uncooked. Conversely, in areas where the airflow is too high, the food product will be burned or overcooked. In such situations, it is desirable to tune the convection oven so that a uniform airflow is obtained.
Many conventional commercial convection ovens having low pressure systems are tuned by attempting to produce a single flow pattern having a uniform flow and temperature distribution within the oven cavity. However, the tuning of conventional convection ovens is difficult, and often a trial and error process, for several reasons. First, convection ovens are used to cook different types and quantities of food products having a variety of sizes, shapes and cooking requirements. Second, the airflow pattern within the oven cavity is highly unpredictable because the energy is stored in the form of velocity rather than pressure. Third, air may not flow through the oven cavity in a uniform pattern depending on the direction and magnitude of the surrounding flow. Accurately tuning a conventional convection oven with a low pressure system is extremely difficult for these reasons.
It is apparent that there is a need for a convection oven with a tuneable airflow pattern within the oven cavity to provide a uniform airflow pattern for an even cooking process.
It is also apparent that there is a need for a convection oven wherein the energy is stored in the form of pressure rather than velocity to provide a predictable airflow pattern.
It is an object of this invention to provide a duct distribution system to produce a high pressure airflow within a cooking chamber of a convection oven.
It is another object of this invention to provide a high pressure airflow that is easily tuneable to a predictable direction and defined pattern to provide a uniform airflow within a cooking chamber.
The above objects and other objects of this invention are accomplished with a duct distribution system for a convection oven having a blower plenum, positioned adjacent and in communication with a cooking chamber, and a duct. In preferred embodiments of this invention, a high pressure convection blower produces a high pressure airflow at about 800 cubic feet per minute (xe2x80x9ccfmxe2x80x9d) at about 2 inches to about 3 inches of static pressure. For other convection ovens having a cooking chamber with a different volume, the high pressure airflow may vary accordingly. For example, the high pressure airflow may range from about 400 cfm to about 1600 cfm.
The duct is connected to the blower plenum and in communication with the cooking chamber. In the preferred embodiments of this invention, the duct extends along at least a portion of the outer back wall and/or a side wall of the convection oven. Preferably, at least a portion of the duct has a plurality of nozzles extending into the cooking chamber. Each nozzle is moveable between an open position and a closed position to tune the airflow pattern within the cooking chamber. In other preferred embodiments of this invention, a plurality of apertures, for example slots, are positioned on at least a portion of the duct.
Preferably, the static pressure within the duct is at least 0.5 inch H2O or at least about 250%, preferably at least about 300% of a theoretical dynamic pressure. The relatively high level of static pressure in the duct allows the airflow though the nozzles into the cooking chamber to be precisely tuned to a definite airflow pattern. Tuning the airflow according to this invention involves closing the nozzles in areas where the airflow into the cooking chamber is too high, and opening the nozzles in areas where the airflow into the cooking chamber is too low.
In one preferred embodiment of this invention, an inlet baffle is positioned between the cooking chamber and the blower plenum. The inlet baffle has a plurality of apertures to provide communication between the cooking chamber and the blower plenum.
The high pressure airflow and duct distribution system in accordance with this invention can be used in any type of convection oven including, but not limited to, gas-fired convection ovens and electrically-fired convection ovens. Further, the gas-fired convection ovens may use a direct-fired combustion system and/or an indirect-fired combustion system having a heat exchanger.
The convection oven further comprises a gas combustion system mounted with respect to the blower plenum to produce or generate combustion products. In preferred embodiments of this invention, the combustion products move into a heat exchange element comprising a plurality of heat exchange tubes. The heat exchange tubes are mounted within the blower plenum and with respect to the high pressure blower.
As the combustion products move through each heat exchange tube, heat is transferred from within the heat exchange tube to a volume of the blower plenum by conduction. Further, the high pressure blower produces a high pressure airflow across the heat exchange tubes to transfer heat from the heat exchange tubes to the high pressure airflow through convection.
The combustion products collect in a header which is connected to an inducer having an inducer fan that draws or induces the combustion products into the inducer. The inducer has a valve which is moveable between an open position and a closed position. In the open position, the combustion products move through the inducer to ambient air through a vent connected to the inducer. Thus, the combustion products do not enter the duct and the convection oven operates as an indirect-fired combustion system.
In the closed position, the combustion products are in communication with the cooking chamber. Thus, the convection oven operates as a direct-fired combustion system and the combustion products directly contact the food product in the cooking chamber during the cooking process.